1. Field of the Invention
This invention relates to odor detectors and, more particularly, to a method and apparatus for shortening the time required to bring such an odor detector to a predetermined initial setting for the next detection cycle by purging a detection chamber containing the odor detector through a controlled operation of an ozonizer and a ventilation fan. In this invention, a plurality of tables may be provided for use with a computer to enable a rapid and efficient recovery of detector readings to the initial setting by reference to a specific table which is selected by an operator from among the tables depending upon certain factors including the identity and concentration of previously detected odorant substances.
2. Description of the Prior Art
Odorimetry plays an important role in the field of quality inspection. For example, objective odor determination can be made in the food processing industries, where the freshness and the quality of comestible products can be determined objectively through use of various odor detectors. An odor detector could also have many other applications such as control of fermentation, analysis of raw materials, testing of alcholic or other drug intoxication, etc. Likewise, there are many uses for such a device in the perfume and cosmetic industries. Gas chromatography has frequently been used for detecting the identity and concentration of odorant substances. This technique, however, has certain shortcomings: (1) Results of detection vary depending upon the particular sampling method used; (2) The detections have to be carried out by a person reasonably skilled in the test; (3) Apparatus useful in such gas chromatography is generally costly; and (4) It takes a considerable time before the results are given.
Various types of odor or gas detectors have been proposed and developed which are capable of reliably detecting minute concentrations of odorant substances. U.S. Pat. No. 4,770,027 to Ehara et al discloses one such arrangement which provides the total concentration of odors emitting from an object such as comestible products as an indication of its specific quality including freshness and maturity. In the U.S. patent, an n-type metal oxide semiconductor is utilized as a sensing means which is heated to a predetermined high operating temperature by an electric heater disposed adjacent thereto. The n-type semiconductor, when heated, is responsive to odor molecules absorbed thereonto. Adsorption of odor molecules will cause electrons to be exchanged between the molecules and the semiconductor surface to cause a change in the electron concentration in the semiconductor. The changing electron concentration varies the electric resistance of the semiconductor thus permitting an accurate determination of the total concentration of the odors.
In order to detect odorant substances using the detector of this type, it is necessary to bring the detector to an initial zero setting where the detector chamber is odorless, prior to starting a new detection cycle. Depending upon the identity and concentration of odorant substances, it usually takes ten to fifty minutes before such initial setting is attained. This will disadvantageously place a limitation on the number of detection cycles accommodated within a certain period of time. If odorant substances of high retentivity have been tested in the previous detection cycle or if a detection was made relatively close to a source of strong smell, the ambient air around the odor detector is "contaminated", or contains minute concentrations of such odors, which may require an unreasonably long time of recovery to the zero setting and sometimes make it impossible to restart detection cycles.
It is a principal object of this invention to provide an improved method and apparatus which enable repeated detections of odorant substances in a quick and efficient manner with a view to overcoming the above-stated shortcomings of the prior art.
It is another object of this invention to provide an improved method and apparatus which can shorten the time required to bring an odor detector to an initial zero setting for repeated and efficient detection of odorant substances.
Yet another object of this invention is to provide an improved method and apparatus which uses an ozonizer along with a ventilation fan to purge a detection chamber prior to the commencement of a new detection cycle.
It is a further object of this invention to provide an improved method and apparatus which utilizes a computer to coordinate ozone generation with activation of a ventilation fan in such a manner as to minimize the time it takes for the odor detector to return to an initial zero setting.
Yet a further object of this invention is to provide an improved method and apparatus in which an operator can select a specific table of optimal pattern for quick recovery to an initial zero setting for a subsequent detection cycle from among a plurality of tables stored in a computer.